Lubricant composition



United States Patent LUBRICANT COMPOSITION George J. Benoit, Jr., San Anselmo, and Andrew D. Abbott, Ross, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application June 29, 1955, Serial No. 518,918

6 Claims. (Cl. 252-417) This invention relates to a superior new lubricant composition. More particularly, the invention is concerned with a novel lubricating oil composition having improved corrosion inhibiting properties.

Lubricating oils in general tend to oxidize and form decomposition products which are corrosive to metals. Since the lubricating oils normally come into contact with metal surfaces during their use, the problem of overcoming this corrosivity is one of major importance.

The increased temperatures, higher speeds and reduced clearances commonly encountered in modern internal combustion engines today serve to promote decomposition and the formation of corrosive products. Furthermore, these engines generally employ alloy metal bearings which are particularly susceptible to corrosion and sometimes exert a catalytic effect on the decomposition of the oil to corrosive products.

Lubricating oils for internal combustion engines, due to the severity of their service, have been compounded with agents such as wear inhibitors, sludge inhibitors and detergents to loosen and suspend the products of decomposition and counteract their effect. Unfortunately, however, many of these agents may adversely aflfect the efiiciency of corrosion inhibitors, and it is a problem to find inhibitors which will function in combination with them.

Many of the most effective oxidation and corrosion inhibitors employed heretofore in lubricating oils contain active sulfur. Such inhibitors have an adverse effect on silver and similar metals which are subject to attack by active sulfur. Since these types of metals are being increasingly employed today in certain important classes of internal combustion engines, as, for example, marine and railroad diesel engines, it is necessary to find inhibitors which contain no active sulfur.

It has now been found that a superior new composition comprising a major portionof an oil of lubricating viscosity and a minor portion, suflicient to inhibit corrosion of an alkyl ester of molybdic acid possesses greatly improved corrosion inhibitingproperties with-out the disadvantages of the lubricant compositions employed heretofore as mentioned above l The general tendency of lubricating oils to become oxidized and corrosive to metal surfaces is efiectively inhibited in the improved lubricating oil composition of the invention. Alloy metal bearings which are particularly susceptible to the corrosive decomposition products of lubricating oils are not adversely affected by the lubricant composition of the invention, even under the more stringent operating conditions encountered in modern internal combustion engines. Bearings of silver and similar metals which are subject to attack by conventional oxidation and corrosion inhibited lubricant compositions containing active sulfur compounds are not harmed by this superior new lubricant composition. This is a decided advantage, since such metals are being increasingly employed in internal combustion engines such as marine and railroad diesel engines;

ice

The novel corrosion inhibited lubricating oil composition of the invention is also outstanding in that it may be compounded with additional agents such as detergents, sludge inhibitors and wear inhibitors without adversely affecting its corrosion inhibiting properties. The composition also apparently acts as a metal deactivator for the common bearing metals such as copper and lead which usually accelerate the decomposition of lubricating oil compositions.

The alkyl esters of molybdic acid which are employed in the lubricating oil compositions according to this invention are conveniently prepared by the usual reaction of a mixture of molybdic acid and aliphatic alcohol. The mixtures are ordinarily heated to accelerate esterification. For present purposes, the alkyl esters of molybdic acid or alkyl molybdates and aliphatic molybdates, as they are commonly called, are preferably prepared by the reaction of aliphatic alcohol and molybdenum. compounds,

such as molybdic anhydride or molybdenum tri-oxide, ammonium molybdate, ammonium paramo-lybdate and molybdanyl chloride.

The alcohols which are reacted with the molybdenum compounds referred to above are preferably aliphatic alcohols containing up to 24 carbon atoms. The alkyl radicals may be straight chain, branched chain or cyclic in nature. Ether primary, secondary or tertiary radicals are suitable, but primary and secondary radicals are preferred for desirable physical properties in oil and apparent elfectiveness. methyl alcohol, ethyl alcohol, is-opropyl alcohol, n-butyl alcohol, tertiary butyl alcohol, n-hexyl alcohol, cyclohexyl alcohol, benzyl alcohol, n-octyl alcohol, 2-ethylhexanol, isooctyl alcohol, decyl alcohol, dodecyl alcohol, tridecyl alcohol, octadecyl alcohol, etc. Ether alcohols such as cellosolve, butyl cellosolve and carbitol may also be employed. Higher aliphatic alcohols are preferred, the term here being used in its commonly. accepted sense as covering alcohols of eight carbon atoms or more. Such alcohols impart desirable physical characteristics to the alkyl molybdates prepared from them. Branched chain alcohols, for example, those derived by the wellknown Oxo process are particularly suitable. Decyl and tridecyl alcohols of this latter type have been found to yield very effective molybdate corrosion inhibitors for the lubricant compositions of the invention.

From their chemical analysis the alkyl molybdates are believed to have the following probable structures showing that they exist in either dimer or trimer forms:

In the above formulae the Rs which may be the same or diiferent, are alkyl radicals obtained from the alcohols already described. Although the polymeric forms illustrated above are preferred for present purposes, the monomeric molybdates are not excluded.

The alkyl ester of molybdic acid is present in the compositions -of the invention in an amount at least sufiicient to inhibit corrosion or oxidation. Small amounts, usually from about 0.01 to 5.0% by weight based on the oil are effective. Proportions ranging from about 0.05

Examples of these alcohols include vention is the fact'that the. corrosion inhibition is obtained 70 andweiglied'to d c V a ,7 mclude'variou's compounded mineral; 111- bric'ating oils of'the'internalcombustion engine type which and paraflinic types.

invention. .They include hydrocarbon or mineral lubri:

cating oils of naphthenic, paraflinic, andmixed naphthenic They may be refined by any' of theconventional methods such as solventirefining-and acid refining. Synthetic hydrocarbon oils of the alkylene polymertype or those derived from coal and shale may also be employed. I Alkylene oxide j polymers and their derivatives such as the propylene oxide polymers and their ethersand esters in which the terminal hydroxyl groups, have been modified are also suitable. Synthetic oils of the-dicarboxylic acid ester type'in'cluding dibutyl adipate, di-Z-ethylhexyl sebacate, di-n-hexyl fumaric polymer, dilauryl azelateyand the likemay be used. Allcyl benzene types of syntheticoils such as tetradecyl benzene, etc., are also included. Liquid esters. of acids of phosphorus including tricresyl phosphate, diethyl esters of decane. phosphonic acid, and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxyand polyaryloxy siloxanes such as. polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils. such as tetraalkyland tetraaryl silicates'of the tetra- Z-e'thylhexyl silicate and tetra-p-tert.-butylphenyl silicate types.

The corrosion inhibiting compositions of this invention are also outstanding in that they are unusually effective 'I'he' following examples are submitted as additional il lustrations of the invention. These examples show the preparation of the various lubricant compositions and the evaluation of their effectiveness as corrosion inhibitors. The proportions given in these examples, unless otherwise specified, are on a weight basis and include both percent and millimoles per kilogram (mM/kg.) of the various additives.

' EXAMPLE I r gm. of molybdenum trioxide (0.348 molelis-dissolved in ml. water and 87 ml. ammonium: hydro.

ide (approximately 28% NHa) in a vessel. This solu tion is addedwith mechanical agitation to 560 gm (2.8 moles) of tn'decyl alcohol and gm. of toluene in a reaction vessel equipped withstirrer, refluxcondenser and thermometer. The contents are refluxed for about 13% hours during which period water of reaction and water 0.78 mole of water was produced. J V

The reaction mixture obtained above is filtered t'o re move about 1 gm. of unreacted' solid. 300 gm. of I50 neutral mineral oil is added, and the contents are then fromthe ammonium molybdate solution are. removed.

stripped to abottom temperature of about 285-300 F".

at about 11' mm. mercury'p'ressurel 495 gm. of product is obtained which' analyzes 6.6% by. weight molybdenum, which means that about 98 of the mol'ybdenumis utilized. V

Using. the procedure outlined in the above example, ad-

ditional preparations ofmolybdates ofmonohydric al cohols,.including preparation conditions, are summarized inthefollowingtable. w

Table l MOLYBDATES or rououvnaroxnoonors [Preparation conditions]- Example II Example III Example IV Example V Charge: 7 V Alcohol n-Octyl Oxo'Deoyl. 0x0 Tridecyl. 0x0 Tridecyl. grams/moles 292/224 530/3;34;-; 1,025/5;12. 705/3.52., (NH4)uM021Oz4-4H2O rams/moles. 100/05 I, M003, grams/moles.. fill/0.417 1l0/0.764 "12/050. NH ,moles 1 .56 2.64-.-..-.'.--- 1.94. j H2O, ml 317 y 234. Xylene, ml. 150.. I Toluene, ml 150(Est;-)' 230' 7 180.

Reaction Conditions: v v v F. Pot Temperature... 320 285-295;... '295*305 285-300. Hours 8-- 14. v 1 6.-.. :16.

, D-lluent Oil 150 Neutral... Soiveggjeflned Mineral .480Neutral... 480 NeutraL. None.

grams 75'-..

Stripping temperature, F./1 mm. Hg. 230-.. 320

Product Analysis:

Percent M0 20.5 1125; Alcohol Recovered, grams/moles H30 Produced, moles.-- Unreaeted Solid, grams.

withoutany noticeable adverse effect on the other addi-, tives thus, permitting more eflicient all-around lubricationof. internal combustion'engines and other types? of mamore-andmorecommonly encountered;

chines. where unusually. severe conditions of service are test. oil in a. 4001 ml. 'lipless Berzelius beaker.

5 stirrei at' 1000K. P;'M. After two'hours alsynthetic naphtlienate catalystis added to provide the catalytic metals normally. encountered in-internal combustion-engines. j The? test i'sicontinue'd 20 hours. The copper-lead stri'p'istlien removed, .rubbed vigorouslywitha soft cloth M V eterminej the net weight loss. The tcstoils' are normally" corrosive to alloy metal'beari'ngs'. Initliisf case the compounded oil (A consists of) a solvent re- 1 V fined SAE 40 mineral lubricating oil baseha ving' aviscosity The effectiveness of thelubricating. oil compositionsiof 60 the invention is shown by their performance in thecop per-lead strip c'orrosion test.- In this test apolish ed cop per lead .stripjis: weighed, and immersed in 300 of c The test oil is maintained at. 340 F. and stirred with a mechanical;

index of 60 and containing 10 mM/kg. of calcium petroleum sulfonate and 20 mM/kg. of calcium alkyl phenate. Compounded oil (B) consists of the same base oil but contains 28 mM/kg. of basic calcium petroleum sulfonate. The results of the tests are shown in the following table. The concentrations of alkyl molybdate employed are given in millimoles of molybdenum per kilogram of oil.

1 Table I1 ephthalic acid in compounded oil (13) As shown by the above test data, the typical compounded mineral lubricating oils which are commonly employed in internal combustion engines give a copperlead strip weight loss of as much as 250 mg. By way of distinction, the compositions in accordance with the present invention containing the same compounded mineral lubricating oil bases in combination with various alkyl molybdate corrosion inhibitors give a weight loss of as little as 1.5 mg. The corrosion inhibiting effect of the alkyl molybdates combined with a phthalic acid corrosion inhibitor such as terephthalic acid is also apparent from the above test results. Negligible losses of as little as 0.9 mg. are obtained through the coaction of the two corrosion inhibitors.

In another test which is a modified version of the copper-lead strip corrosion test described above, the effectiveness of the corrosion inhibited lubricant compositions according to this invention in respect to rubbing surfaces is demonstrated. In this test, which is commonly termed the interrupted copper-lead strip corrosion test, the same procedure is followed as in the copper-lead strip corrosion test, except that the test is interrupted at four-hour intervals to insert a new copper-lead strip. The test results are then given in the cumulative weight loss of all the strips. By changing the strips during the test, a fresh, clean metal surface is periodically exposed to the corrosion inhibited composition. Thus, the wiping effect obtained in rubbing metal surfaces such as bearings is simulated, and it is shown what happens when any protective film laid down on the metal surface during operation is removed.

Table III INTERRUPTED COPPER-LEAD STRIP CORROSION TEST Total Additive Copper-Lead Strip Weight Loss (mg.)

None-compounded oil (A) alone 7 mM/kg. decyl molybdate in compounded oil (A) 20 mM/kg. tridecyl molybdate in compounded oil (A) None-compounded oil (B) alone 10 mM g. trideeyl molybdate in compounded oil (B).-. 10 in /kg. trldecyl molybdate and 0.10% by weight terephthalic acid in compounded 011 (B) Approx. 700

Approx. 700

The lubricating oil compositions illustrative of the invention are also evaluated for their effectiveness as inhibitors in gasoline-type internal combustion engines. This test is conveniently termed the L-4 Strip Corrosion Test because of its correlation with the L-4 Chevrolet Engine Test referred to in the CRC Handbook, 1946 edition, Co-ordinating Research Council, New York, New York. In the test the same apparatus and conditions as described in the above copper-lead strip corrosion test are employed with two essential modifications. The temperature is maintained at 295 F. to simulate lower temperatures encountered in gasoline engines, and a synthetic naphthenate catalyst is used containing lead,

as well as the usual catalytic metals, in further duplica-.

tion of gasoline engine operation. The reference oils are conventional compounded mineral lubricating oils of the types described in the above tests. The results of the tests are as follows:

Table IV The test results shown in the above table illustrate the effectiveness of the lubricant compositions according to this invention under low temperature operating conditions. Corrcsivity of compounded lubricating oils generally employed in internal combustion engines runs as high as 250.0 mg. copper-lead strip weight loss. On the other hand, the compositions of the invention containing small amounts of alkyl molybdate reduce the corrosion loss to as little as 9.2 mg. This desirable effect is also obtained when the alkyl molybdates are employed in combination with other corrosion inhibitors such as terephthalic acid.

The nature of the improved lubricating oil compositions of the invention and their effectiveness should be readily apparent from the many illustrations given above. Oxidation and corrosivity in the compositions are definitely inhibited to a very substantial degree. Particularly corrodible metals such as engine alloy bearings of copper, lead, and the like, as well as bearings of silver, are not adversely affected. This is indeed remarkable, since the problem of devising lubricant compositions uniformly noncorrosive to both types of bearing metals has long confronted workers in the art. As shownby the actual tests set out above, the advantages of these improvements are obtained without loss of other desirable properties of the lubricant compositions.

Although the compositions of the invention have been primarily described as crankcase lubricants for internal combustion engines, they are also useful as turbine oils, hydraulic fluids, instrument oils, constituent oils in grease manufacture, ice-machine oils, and the like.

The OX0 alcohols referred to in this application are a well-known class of alcohols derived by the OXo process of reacting olefins with carbon monoxide and hydrogen. Thus, the OX0 decyl alcohol is obtained by the reaction of an olefin of 9 carbon atoms, such as propylene trimer, with carbon monoxide and hydrogen. The OX0 tridecyl alcohol is a 13 carbon atom alcohol obtained by the reaction of an olefin of 12 carbon atoms, such as butene trirner or propylene tetramer, with carbon monoxide and hydrogen. These alcohols, which are well known. in the art, are primarily characterized by a branched chain structure in the alkyl group.

We claim: 1

" 1. QA lubricantcomposition comprising a major portion of an oi1 of lubricating 'Yiscosity" and a minor portion, sliifieient to inhibit corrosion, of an al kyl monohydric alcohol ester of naolybglic acid in which the alkyl group contains from 8 to 24 carbon atoms, saidester being in monomendimer'and trimer forrns.

2." A lubricant composition comprising a major portion of anoilpf lubricating viscosity and afininor portion, suflipient-to inhibitycorrosion of tridecyl molybdate,'said in monomer, dimer and trimer forms.

trideeyl molybdate being a tridecyl ester of molybdic acid 35 A lubricant composition comprising a major portion 7 of gani-oil -of lubricating Viscosity anda minor portion, snflicient to inhibit corrosion, of tridecyl molybdate and t efeph thalic" acid, said tridecyl mo'lybdate being a tridecyl ester "of mol'ybdie acid in monomer, dimer and trimer forms. I s l 4. A lubricant composition -lc ornprising a major portion of a mineral lubricating oil and a minor portion, sufficient to inhibit corrosion, of an alkyl monohydric alcohol ester of molybdi'c acid said ester being in monomer, dimer and trimer fonns.

nsme 1 aadfiim fa 1 Lanna-@995 bri to inhibit corrosion, of tridecyl molybdate and 'ierifli' thalic acid, said tridecyl niolibdate being a tridecyl ester of y d id in mcmo c slime and mate forms- 1 References Cited in the file this 'VUNITED STATES PATENTS 7 sea wa we waesansmr l Q r insrelt y i a 9A 7 to inhibit corros on, of tnldecyl; 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PORTION OF AN OIL OF LUBRICATING VISCOSITY AND A MINOR PORTION, SUFFICIENT TO INHIBIT CORROSION, OF AN ALKYL MONOHYDRIC ALCOHOL ESTER OF MOLYBDIC ACID IN WHICH THE ALKYL GROUP CONTAINS FROM 8 TO 24 CARBON ATOMS, SAID ESTER BEING IN MONOMER, DIMER AND TRIMER FORMS. 